Valve construction for pneumatic tools



E. W. STEVENS l VALVE CONSTRUCTION FOR PNEUMATIC TOOLS Filed July 25, 1921 Feb. 1o. 1925,.

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Patented Feb. 10, 1925.

UNITED STATES PATENT OFFICE.

EDWARD W. STEVENS, OF DETROIT, MICHIGAN, ASSIGNOR TO CHICAGO PNEUMATIC TOOL COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

VALVE CONSTRUCTION FO'R PNE'UMATIC TOOLS.

Application filed July 25,

To all whom t may concern.'

Be it known that I, EDWARD WV. STEVENS, a citizen of the United States of America, residing at Detroit, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Valve Constructions Jfor Pneumatic Tools, of which the following is a specification, reference being had therein to the accompanying drawings. l

The invention relates to pneumatic tools of that type in which the valve is in the form of a sleeve through which the piston reciprocates and in which the shifting of the valve is effected by the pressure of trapped fluid compressed by the piston in its return stroke. With such type of construction it is highly important to avoid leakage, tending to neutralize the differentialpressure and thereby interfering with the quick and positive shifting of the valve. This is not difficult to attain when the construction is newbut the wear incident to use enlarges the clearances and destroys the proper balance. I have therefore devised a construction which is not so dependent upon close clearances and will remain operative after the working surfaces are worn.

In the drawings:

Figure l is a central longitudinal section through the tool in one position of the piston and' valve;

"Figure 2 is a similarview of the piston and valve in different positions;

Figure 3 is a longitudinal section in aV plane indicated by line 3-3 of Figure l.

A is the casing or barrel of the tool containing the reciprocating piston B. C `is the sleeve valve surrounding the piston and D is a. cylindrical valve casing engaging a counterbore in the main barrel. The valve C hasa tubular body portion, the internal diameter ofwhich corresponds to that of the barrel. The opposite end portions of this tube slidably lit the portions E and E of the casing D, which are of corresponding diameter, and intermediate these end portions are the pairs of outwardly projecting annularlanges F, F, G, G', respectively slidably engaging portions H and I of the casing, the portion Ibeing of greater diameter than the portion I-I. Adjacent to the iange F on the outer side thereof are a series of fine ports J extending through the sleeye andbetween the angesl andA GK are 1921. seriai No. 487,356.

a series of large ports K. The casing D is further provided with a series of annular ports L, M and N, the first surrounding the portion E and the others surrounding the portion I. The port L is connected with the supply passages O for the motive liuid, which extend longitudinally through the walls of the casing D intersecting said port L. The port M is connected by a passage P with the outer end of thebarrel and the port N is connected with an exhaust passage Q. The casing is further provided with the passages R, S and T. The passage R leads from the supply passage O to a port in the portion H. The passage S leads from the end of the portion I to a port S in the barrel, which is controlled by the movement of the piston, and the passage T communicates with the portion I of the barrel intermediate its end and the channel N and connects with the supply passage O.

With the construction as thus far described, when the valve is in the position shown in Figure l, live air from the supply passages will pass throughthe annular port L into the barrel, driving the piston forward or towards the tool, while the air which is in front of the piston is exhausted through the passage P, channels M and N and exhaust port Q. When the piston has over-ridden the port S', air from the barrel passing through said port and the passa-ge S will develop a pressure upon the lower face of the iange G and as this area is in excess of the area of the flange F, the valve will be shifted rearward. This will register the groove N between the flangesG and Gr with the exhaust port Q, permitting the exhausting of the pressure above thepiston in the barrel through the ports'K. The shifting of the valve also moves the iiange G above the port T so that when the pressure in the barrel drops, the pressure operating against the ange G is still maintained by live air entering through the port T. kThe valve in its shifted position, or as shown in Fig. 2. opens communication between the passage R and the channel M, thereby permitting the air to pass through the passage P below the` piston tov cause the return of the same. rPhe valve maintains this position until` inthe return stroke of the piston the exhaust port-s K are sealed and the air which is trapped above the piston is compressed; This highly compressed air ,passes through the small (iii ports Ji towthc uppersider7 of.' thewflange and While-.thc area of this flange.iss/lessA than the area of the flange G, the high-en. fluid. pressure von .the vflange .F Will overcome the lower fluid` pressure on the flangevG" and shift,v the valve.

The construction -aloeve'described:has"` heretofore been used7 but l have devised certain improvements which arexasefo-llowsfi-I One improved feature in the arrangement ofi ahy-pass or air channel 2U leading #from thier upper i' end? of the =ba rrelf to f al port* U adjacentto the flange Ff.' Another' feature is* the: placingfof'f af constantly' openv but" re-` Y strictedJporti'V between-'the airv supply' and* thefuppe-r end .off the barrel-,fitbeing'- usual toi place'su'elrla port'directly'adjacent to the flange VF.. lVith-'sueh construction;.Wlieirthef valve? is fin" position 'shown in Figure" 2'" and While-'the piston isf-fon its 'upwar'dl stroke and before l' it has se'ale'd'f the exhaust ports Kg thechannel-U andi: port 'U' 'supplement' the* pixrtsaJ.,y in.' exhausting the@ air Whiclr mavv leaklfroin' the@ port` E between' the'j valve*V sleeve' andvits casinga This avoids-building' up'i'pressurel-i on the fla-nge E se than even whereetliere isleak'age from theotlier' end of: the? valveV slee-ve, y the pressureacting upon therllange Gf will 'stilllcefin' excess 'off the' pres'sureiarctingupon the flange Ff ieL'nothe-l1t advantage ofJ the construction is; thatfl'lighly compressedacir Whiclnistrappedin the upperl 'end off the. barrel isA byipassedf through therchann'el andport U to'build up1pressure* up'o'nthe flange"v F for shifting the valve. Still another' advantage ist that by dispensing with: the'V constantly open port' leadingz'to the flangefR-the portsJ andU" need.' to take"y care only' of' the air leakingl aboutthevalve sleeve and arerelievedfrom the necessity' of'exhausting air froinsaidI constantly" open port'. The' totalefi'eot= is to provide a: valve1 ofv exceptionally' quick and: positive* response` and" one' Which will3 f remain operative after.' long ser-vice:

VhatE-Iclaiin as mylinvention is;

1'.. The i combination With a re'c'iprocatorypiston', of' barrel thereforfg; exhaust' ports in` saidbarrielg a sleeve valve surrounding and'fitt'ingf said piston. and slidably engage ing'a'i recess in said barrel,v annular'flangcs of; differenti diameters surroundingzr said if'alv'e and? engaging' portionsroff said recessof corresponding` diameters, main' exhaust" ports.g through said* valve intermediate said' flanges and.' cooperating? Wit-h1 thefexh'aust portsiin said barrel', restrictedexhaust portsthirougli saidvalre adjacent tothe smaller flange for exhausting'iiuidf' pressure in: the' portion! of the' recesslengaged byA said' flange; ai channel for supplyingll lluid"V pressure from an intermediateportion ofthe barrel tothe portioir ofv tlie'recc'ssl engaged' b v the larger of'fsaidxflanges and channel for 'connecting tlierportonA ofi' the` recess#engaged"- by the saidL reeess-1wl1en the pressure Within the barrel is exhausted.

2.' Ther'coinbination with a reciproca-tory piston, a barrel therefor and a sleeve valve surrounding and fitting; saidi piston and' slidably1u engaging i' aE recess'l inf said f barrel, annular flanges: of different diameters-l' surrounding said' valve' and' engaging' por:V

tions of said recess L ofi` corresponding diam# eters, Inaiinexhaust ports th'rOuglrsaid 'valve' coopera ting With an exliaustportfin ther-baall rel,y an airl supply: portL to' the' 'barrel con'-v trolled by a portion offsafidV valve; re=Y stricted exhaust ports througlr-,saidfvalizel adjacent to'-tlie. flangee'of smaller-fdialinet'erf for exhausting leakage fronn saidfsup and as channel connecting` the-portion -o fithe-y recess engaged-by said lasti-mentionediflangef With the end offfthe' barrel for transferring f the trapped? fluid compressedbyf'thef' piston' l;

While'said restrietedexhaust ports are seal ed fand' for' exhausting" the-'- leakagel tofsand*l recess' W'lieni thel connected portion ofi said barrel is open' to'itlielmain' exhaust;

3J The combination With-'al reciprocatorypiston; a- 'barrel2 thereforfand" as sleevef valvesurroun'ding and f fitting? saidI pistoir and* slidabljf engaging-l arecessein -said barrel; ane annular supply' porti fr 'sa-idfV 'barrelv alternately opened thereto 'and sea-led by' a" pon# tionl ofthex va'lve,- an annular* flange 1- sur rounding the valve engagingfa portionloff'the recess; of corresponding? diameter, restricted exhaust' ports' through said'x valve: adjacentA to said annular ange for exhaustingthelealrage' from said supplyl portintof said recess While 'the' pressure-1in the c'ommunicat' ing"portionfof' "thebarrelf issexhausted;`4 and a channel connecting*tl1e1po'rtion= off' the recess adjacentL to"- said flange rwith the end of the bar-relffortheltransfer of fluid coin-t pressed by' the' piston- WhileL said restricted' exhaustv ports: are sealed therebyfand for fo'rn'iing-f an auxiliary exhaust# f'or leakage into` said recessz Wli'ile. the pressure inv the' connectedf portion: of? the barrel is 'exheaistediy fl. The-y combination with'Y a rec'iprroeatery4v piston,` aebarrel' therefor' and a1 vsleeveevalvef surroundingT and fitting said 1 piston-y and slidably-fengaginga 1ecessi11 saith barrel; an annular' pressureAV supply" port' for4v said barrel alternatelycovered; and' unco-vi eredlbyafpo'rtioir of said vailifefan annular flange surrounding said-"valveJand'' engaging a portion: of! said recess' ofi corresponding" diameter",- restricted exha'ustvports through saidvalveadjacentto Vsaidiflange-forexhaust leakagefv-to said:` recess frein.` saidi' 'emular supply port, a. channel connecting said recess with the end of said barrel for transferring the trapped iuid compressed by the piston to produce a shifting pressure for the valve, said channel also constituting an auxiliary exhaust for leakage pressure When the pressure in the connected portion of the barrel is exhausted, and a leak port from the supply pressure to said end portion of the barrel for building up starting pressure.

5. The combination of a barrel having a piston chamber, a. piston reciprocating therein, a reciprocating sleeve valve defining a part of said piston chamber# and governing the admission and exhaust of the motive iuid for reciprocating the piston, said valve being operated in one direction by motive fluid compressed bv the piston in the rear end of the piston chamber on its return stroke and having an external pressure area, and means for luy-passing such uid compressed by the piston and discharging it against such pressure area.

6. The combination of a barrel, a piston reciprocating therein, a sleeve valve surrounding` said piston and forming a portion of said barrel, said valve controlling the admission and exhaust of the motive fluid for reciprocating the piston, opposed differential areas on said valve, and means for subjecting said differential areas to fluid pressures derived from opposite ends of the barrel including a by-pass to the smaller area for the fluid compressed by the piston in its return stroke.

7. The combination of a barrel, a piston reciprocating therein, a reciprocating valve governing the admission and exhaust of motive fluid for reciprocating the piston and operated in one direction by motive Huid compressed by the piston on its return stroke in the rear end of the barrel, said valve having an external pressure area, means for by-passing such fluid co-mpressed by the piston and discharging it against such pressurefarea, a. Hui-d supply passage, and a constantly open restricted port between said fluid supply passage and the end of said barrel in which the iiuid is compressed.

In testimony whereof I afiix my signa- EDVARD lV. STEVENS.

ture. 

